High voltage circuit breakers



Sept. 4, 1956 J, D. WOOD ET AL 2,761,934

HIGH VOLTAGE CIRCUIT BREAKERS Original Filed Jan. 11, 1947 8Sheets-Sheet J.

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Sept. 4, 1956 J. D. WOOD ETAL HIGH VOLTAGE CIRCUIT BREAKERS OriginalFiled Jan. 11, 1947 a Shee ts-Sheet 2 Sept. 4, 1956 J. D. WOOD ETAL HIGHVOLTAGE CIRCUIT BREAKERS ori in-a1 Filed Jan. 11, 1947 8 Sheets-Sheet 4267 HfifilfifilflfiHHHHHHMFIHHHHHHHHHHHHHHHHITI I N V EN TORJ'. ddserg.D [7000 442 mm? 5'. dam/14 BY Sept. 4, 1956 J. D. WOOD ETAL HIGHVOLTAGE CIRCUIT BREAKERS 8 Sheets-Sheet 5 Original Fileddan. 11, 1947 Set. 4, 1956 .1. D. WOOD ETAL HIGH VOLTAGE CIRCUIT BREAKERS 8 Sheets-Sheet6 Original Filed Jan. 11, 1947 o 3 NR ama #0 U Q O "U Q s @m o 0 o q :33Q 0 2 c I N V EN TOR) \/dsP// J2 w By mwj dam/4L4 OXM a M Sept. 4, 1956.1. D. WOOD ETAL HIGH VOLTAGE CIRCUIT BREAKERS Original Filed Jan. 11.1947 8 Sheets-Sheet 7 Original Filed Jan. 11, 1947 8 Sheets-Sheet 8Sept. 4, 1956 J WOOD ETAL 2,761,934

HIGH VOLTAGE CIRCUIT BREAKERS IN V EN TORS dOJEP/l D. W000 irre/vfUnited States Patent HIGH VOLTAGE CERCUIT BREAKERS Joseph D. Wood,Straliord Village, and Arthur Stephen Caswell, Philadelphia, Pa.,assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa.

Application May 7, 1947, Serial No. 746,554, now Patent No. 2,646,481,dated July 21, 1953, which is a division of application Serial No.721,648, January 11, 1947, now Patent No. 2,613,299, dated October 7,1952. Divided and this application September 4, 1952, Serial No. 307,843

6 Claims. (Cl. 200-147) Our present invention which is a division ofUnited States Patent No. 2,613,299, issued October 7, 1952, and UnitedStates Patent No. 2,646,481, issued July 21, 1953, relates to highvoltage high capacity circuit breakers, and more particularly to circuitbreakers having an interrupting rating of 50,000 kva. and better in anyvoltage range between 2300 and 5000 volts and at current ratings of 600and 1200 amperes.

Essentially our invention is directed to the production of high voltagehigh capacity air break switchgear in such a manner as to provide theincreased interrupting capacity required by means of the simplestelements which are manufactured and assembled by mass production methodsin the most economical way.

In order to achieve this result, it has been necessary to design ournovel circuit breaker so that the various elements thereof may bemanufactured in individual relatively inexpensive single unitary circuitbreaker by a minimum number of operations.

Our novel circuit breaker also by reason of its simplicity of design andeconomy of operation lends itself to simplified and economicalconstruction, and thus overcomes one of the primary objections toair-break circuit breakers of this rating.

Air circuit breakers of high kva. interrupting capacity have heretoforebeen very expensive in design and construction utilizing castings andwelded parts and have usually been custom-built for a particular jobrather than made in a particular grouping or line for particularinterrupting capacities.

Our novel construction fabricated entirely from shut or bar stock intomany sub-assemblies and using no castings lend itself to mass productionmanufacturing methods which together with simplicity in design reducethe cost of the high voltage high capacity breaker to a point where itscost compares favorably and at times is even less than many low voltagerelatively low capacity circuit breakers.

In a high voltage high capacity breaker the first and most importantstep involved is the construction of the are chute and of the arcblow-out mechanism so that any arc which is drawn between the contactsas they open may be readily extinguished before damage to the breaker orto the circuit may occur.

Our novel circuit breaker includes a simple unitary arc chute structuremade as a single unit provided with a disconnect and so arranged that itmay readily be mounted on the circuit breaker and connected thereto orremoved therefrom as a whole without the necessity for special tools.

Our novel are chute thus combines the essential ideas of simplifiedconstruction for greater economy and simplified arrangement in the formof a single unit assembly which may readily be mounted on any circuitbreaker of the class to which the arc chute is to be applied. The arechute may readily be removed for inspection of the contacts of thecircuit breaker or for replacement or re- 2 ,761,934 Patented Sept. 4-,1956 pair of any part that may require such replacement or repair.

In a high voltage high capacity circuit breaker, one of the mostimportant problems is the provision of proper insulation and theavoidance of any dielectric breakdown which may occur in the operationof the circuit breaker.

An important object of our invention, therefore, is the novelarrangement of the arc chute so that the front arc runner or arcing hornis entirely disconnected from the back terminal in any position of thecircuit breaker, whether closed or open. This is achieved by soarranging the movable arcing contact that it may transfer the arc to thefront are runner solely by reason of its proximity thereto during aportion of the opening movement; the arcing contact at the completion ofthe opening movement moves suificiently far away from the front arcrunner so that there is no connection or likelihood of any connectiontherebetween. This front arc runner is entirely disconnected and thefront of the arch chute member is completely safe for handling evenwhile the circuit breaker is racked into position.

Our novel arc chute is supported and carried entirely by our novelblow-out mechanism which in turn is secured to the main panel of thecircuit breaker in a readily movable manner hereinafter described. Theblowout mechanism thus constitutes a unit sub-assembly by itself.

The blow-out mechanism comprises essentially a U- shaped iron structure,the base of which is surrounded by the blow-out coil and the legs ofwhich extend out perpendicularly to the panel on which the circuitbreaker is mounted. These legs of the U-shaped iron structure carry thearc chute; and the arc chute may be slid on to or olf these legs forplacement or removal.

The upper back connection stud and stationary contact elementsconstitute a single unit sub-assembly which may readily be mounted onand removed from the back panel.

The lower back connection stud and the movable contact arm with its linkeach constitute a single unitary sub-assembly which may also as abovepointed out be readily mounted on and removed from the circuit breakers.Both the upper and lower back connection members have secured theretothe back disconnect contacts which are part of the same assembly.

The mechanism assembly which includes all of the operating membersconstitutes a single sub-assembly which may readily be mounted on thecircuit breaker panel and disconnected therefrom and which may beconnected to the movable contact arm by passing a single pin through theconnecting link.

The other individual assemblies which may be manufactured separately andindividually mounted on and removed from the circuit breaker include theracking and indicator assembly, the control panel assembly and the tripunit assembly. Other assemblies and relays may be added or removed asdesired in order to complete the individual circuit breaker.

Outstanding features of our novel circuit breaker include:

1. The simplicity of construction in the vicinity of the contact.Bearings and other cooperating parts required for proper contactpressure are located at or near the contact pivot point. This reducesthe momentum of the moving parts resulting in faster opening and lighterduty on the bumper. These parts are also less exposed to make possiblethe construction of a narrower arc chute.

2. Reduction in the diiference of impedance between the main and arecontact current paths sufliciently eliminated the necessity for a shuntcontact. The arcing contact alone afiords a maximum of protection forthe main contact.

3. Our novel device makes possible the complete elima ination ofpigtails with all of the attendant difficulties involved in theconstruction operation and maintenance of pigtails.

4. Our novel construction also permits the elimination of a returncurrent loop required to produce a blow-on arc contact. This currentloop would not only increase the impedance between the arcing and maincontacts but tends to blow ionized gas down to the mains making possiblea restrike to the mains. A small insulation barrier has been used toprevent just this condition on some breaker designs. Our novel devicemakes such an insulation barrier unnecessary.

As above pointed out, the blow-out iron circuit is made up of a corearound which the blow-out coil is Wound; to the ends of the core areattached the side plates which project forward nearly the entire depthof the arc chute. These plates also act as slides or runners andsupports for the are chute and the complete assembly is thus sup porteddirectly on the back panel support.

Heretofore in the construction of blow-out mechanisms, it has been foundthat a concentration of flux at the coil end occurs with solid sideplates so that only the coil end of the arc chute is used.

Accordingly another object of our invention is the novel arrangement ofthe blow-out iron in such a manner that the flux is relatively evenlydistributed over all of the side plate area so that the entire arc chuteis used.

In actual operation we have found that an economical combination of fourA2 inch thick plates on each side gave a fairly even flux distributionover the full length.

In addition, and in order to enhance the blow-out effect, auxiliaryblow-out iron plates are attached to the runner strip on each side ofthe arc chute and divert part of the main blow out field down into thevicinity of the contact.

By this novel construction the blow-out structure and the arc chutestructure are mechanically separated and independent of each other sothat the arc chute is much lighter and easier to remove for inspectionand so that the blow-out construction acts as a support for the arcchute.

Accordingly an object of our invention is the construction of a highcapacity high voltage circuit breaker, capable of interrupting arcs of50,000 kva. capacity or even better, and economical in design andconstruction, capable of unit sub-assembly manufacturing operation; andso reduced in cost that its price may compare favorably and at timeseven be lower than that of many lower voltage circuit breakers on themarket today.

In actual practice, the commercial circuit breaker hereinafterdescribed, which was designed for 50,000 kva. interrupting capacity hasbeen subjected to four successive tests at 63,000 kva. interruptingcapacity although standard practice requires only two successive testsat the full rate interrupting capacity.

Furthermore, by changing the material of the arc chute plates it wasdiscovered that the interrupting capacity of the breaker was greatlyincreased. For instance, in one case, a breaker that would interrupt 65mva. was found capable of interrupting current in excess of 125 mva. byno other change except the change in the material of the arc chuteparts.

It is therefore an object of this invention to provide superiormaterials for are chute parts.

In addition, in high capacity circuit breakers which are designed tointerrupt arcs of substantial kva. it frequently occurs that theblow-out mechanism will elfectively move the are into the arc chutecausing it to be extinguished at or near the full rated interrputingcapacity, while the blow-out mechanism is not able to perform the job ofmoving the are up into the arc chute at very low current valuesrepresented by the charging currents of transformers or cables owing tothe fact that the flux through the blow-out mechanism or coils is verylow and ineffective. This has resulted, in some prior art circuitbreaker construction, in the addition of further devices such as puttersand the like to assist the blow-out coil in performing its operation.Alternatively the prior art blowout coil has been provided withsufficient turns to obtain the required ampere turns even for lowcurrent failures. Such prior art devices have thus utilized theexpedient simply of assisting an ineffective construction by addingadditional construction thereto rendering it unnecessarily bulky.

Another and primary object of our invention is the arrangement andconstruction of .the blow-out mechanism of our novel circuit breaker sothat it may move an are at low interrupting current as well as an are athigh interrupting current properly into the arc chute so that the samemay be extinguished; the said blow-out mechanism operating for thispurpose over the entire range of interrupting capacity of the circuitbreaker without the necessity for additional aid or other expedients.This we achieve in part by passing only a portion of the arcing currentthrough the blow-out coils, the percentage of such current decreasing asthe fault current increases. For very low value currents, we provide aseparate arc chute.

The foregoing and many other objects of our invention will becomeapparent from the following description of the drawings in which Figure1 is a side view in perspective, partly broken away showing our novelcircuit breaker assembled and mounted on a truck.

Figure 2 is a side, back view, in perspective, showing our novel circuitbreaker mounted on a truck with the interphase barrier in position.

Figure 3 is an enlarged side front view in perspective partially brokenaway showing the lower terminal assembly, upper terminal assembly, theblow-out coil assembly and the movable contact bridge assembly.

Figure 4 is a detail of the construction of the front end of lowerterminal of our novel circuit breaker.

Figure 5 is a side view of the arc chute assembly.

Figure 6 is a front view of the arc chute assembly.

Figure 7 is atop view of the arc chute assembly.

Figure 8 is a side view of the interphase barrier.

Figure 9 is a front view of the interphase barrier.

Figures 10 and 11 are schematic views illustrating successive steps inassembling our novel circuit breaker.

Figure 12 is a perspective and partially exploded view of a portion ofthe arc chute of our novel circuit breaker.

Figure 13 is a schematic view showing the current flow when the circuitbreaker is opened on a relatively low current, and hence, has relativelylow blow-out flux.

Referring now to Figures 1, 2 and 3, our novel circuit breaker is shownpreferably mounted on a movable truck. The movable truck comprises aback main supporting structure which includes the vertical supportmembers 10 and 11 connected together and interbraced at the lower end bythe masonite panel 12 and at the central and upper portion by thecross-bars 13, 14 and 15 which are connected as shown, in anyappropriate manner, as for instance by bolts and nuts to the verticalmembers 10 and 11. The lower ends of the vertical members 10 and 11 areprovided with bearings 17 and 18 for the shaft 19 which carries the rearwheels 20 and 21 of the truck.

'The vertical members 10 and 11 together with the cross bracing elementsabove described and the wheel 20 and 21 constitute a single unitarymember of assembly.

Certain of the assemblies are standard and require no specificdiscussion here. Thus, the control panel assembly 47 and the trip unitassembly 48 may be substantially standard units which require nospecific description. Also, the control switch contacts indicatedgenerally at 70 of Figures 1 and 2 and the grounding contacts 71, 72 ofFigures 1 and 2 may be standard units. The essential elements as abovepointed out with respect to these units is the unit assembly arrangementwhich is possible with the construction herein shown.

The rear end of the operating mechanism assembly 46 is supported on thecross bar 74 which is held by the bolts 75, 75 across the top of thelower panel 12. Cross bar 74 also provides means for supportingadditional assemblies. The specific novel assemblies or sub-assembliesshown in Figures 1 and 2 and forming an essential part of the novelcircuit breaker here shown are the operating mechanism shown in Figure1, the lower terminal assembly shown in Figure 4, the upper terminalassembly of Figure 3, the movable contact arm or bridge assembly ofFigure 3, the blow out assembly of Figure 3 and the arc chute assemblyof Figures 5, 6 and 7. The specific operation of these individualassemblies renders possible the entire high speed high capacity circuitbreaker which our novel unit embodies. Additional assemblies whichfacilitate the operation are specifically described in connection withFigures 8 and 9 which show the interphase barrier assembly.

The various assemblies above mentioned will be described in order, goingfrom the bottom toward the top of the circuit breaker without specificemphasis on any one of the assemblies over the other.

'It must be emphasized, however, that an important feature of thecircuit breaker is in the novel arc chute construction in conjunctionwith the novel blow out construction.

The operating mechanism utilizes as closely as possible the simpleprinciple of the lever operated switch with only enough addition theretoto provide automatic response to overcurrent conditions in order to tripthe circuit breaker and also to provide a solenoid closing means. Thesimplification ofthis operating mechanism makes possible the productionof the inexpensive circuit breaker herein described.

Thus, while the arc chute assembly and the blow-out assembly makepossible the high capacity operation and high speed operation which areessential to the operation of the circuit breaker as a whole, thesimplicity of the other assemblies makes possible the economical andefficient construction.

The individual unit assemblies facilitate storage of parts preparatoryto final assembly and thus make it possible to. fill orders quickly.

Thus the first sub-assembly which consists of the back panel and theback wheels 20 and 21 is essentially a simple flat member which mayreadily be stored and does not take up any substantial amount of space(see also Figures 1 and 2).

Heretofore, the difficulty encountered in pre-manufacture ofsub-assemblies in anticipation of future orders resided in the fact thatthe main frame of the circuit breaker or other switch gear usually Wasas big as the circuit breaker itself, so that the manufacture andespecially the t storage of the main frame presented the same problem asthe storing of an entire circuit breaker. No real economy was effectedby pre-manufacture of the main frame since the entire circuit breakercould be stored just as readily.

By means of our novel device, the back panel and the rear wheels of thetruck which constitutes a single fiat structure may readily be storedawaiting specific orders for assembly of specific circuit breakers.

The truck structure is completed by means of a lower or bottom platform23, which carries a front wheel 24 in the front swivel 25 (Figures 1 and2) The bottom platform 23 is secured at the rear end to the lower end ofthe. vertical members 10 and 11 above the bearings 17 and 18 for therear wheel. The bottom platform 23 in connection with the back panelform the vertical supporting members 10 and i1 and their interbracingstructure and taken together with the rear wheels 20 and 21 and thefront swivel wheel 24 comprises the truck or mounting for the circuitbreaker constitutes a single sub-assembly which may readily be storedwithout requiring any additional space and which may readily be attachedby two screws to the lower end of the vertical members 10 and 11.

This type of unitary sub-assembly construction which may readily beinterconnected with other elements in order to make a complete truck,facilitates modification and of variation of sub-assemblies in order tomeet the specific orders.

Thus in the event various control elements must be multiplied to asubstantial extent in the final circuit breaker thus requiring perhaps acustom built lower platform 23, this lower platform 23 may be built tothe unique specifications of the customer and may then be combined withthe standard back panel construction which is kept in stock. However,the entire truck construction inctuding the first and secondsub-assemblies above described are built in full anticipation of allrequirements to which the particular circuit breaker may be put, so thatparticular custom made back or bottom portions of a truck will berequired only in exceptional cases. The upper terminal assembly 30, andthe lower terminal assembly 31 for each of the three poles is formedfrom a single bar of copper of rectangular cross section appropriatelyinsulated by phenolic insulation as described more specificallyhereinafter in connection with Figure 3. The terminal assembly elements30, 31 are carried by the vertical supports 10 and 11, as well as thecentral vertical support 32 which is carried between the lower masoniteplate 12, and the upper cross bar 14, as shown in Figure 2.

Each of the vertical members 10, 11 and 32 is recessed at 33, 33 toreceive the terminal members and accurately position the same. Each ofthe terminal members is provided with a side plate or flange 35hereinafter more specifically described in connection with Figure 2.

Each of the vertical reinforcements 10, 11 and 32 is a rectangular steelmember, so that while the recesses 33, 33 are cut out in the verticalreinforcement they are incised only in the portion of the rectangularsteel member which is normal to the back panel 56. The legs of each ofthe rectangular members 10, 11 and 32 carry the bolts 36, 36 whichengage the flange members 35 of the terminal element. Thus it will beseen that two bolts or screws 36 are all that are necessary to secureeach of the terminal elements in place, these bolts being locked insecured position by the nut 37 as shown in Figure 2.

Each of the upper and lower terminal assembly mem-. bers 3t] and 31 alsocarry the spring biased disconnect contact elements 38, 38 alsohereinafter more specifically described in connection with Figures 1 and2, but shown also in Patent Number 2,029,028. The intermediate cross bar13, which is secured to the vertical members it), 11 and 32 by the boltstil, also carries at its outer end the wheels 42 on an appropriate shaftextension thereof, the said wheels 42 cooperating with appropriatetracks in the compartment to guide the truck into and out of thecompartment properly.

The racking and indicator assembly shown generally at 4.3 of Figures 1and 2 also carries the front wheels 54, 44 to ride on the guide tracksof the compartment in which the circuit breaker is housed.

The movable contact assembly shown generally at 50 of Figures 1 and 3 isconnected at its lower end to the lower terminal assembly 31 in themanner hereinafter described, and is provided with a link 51 which isconnected to the contact operating arms 52 projecting up from theoperating mechanism assembly 46. The movable contact bridge assemblywhich of course has as many poles as there are upper and lower terminalas semblies, three in the particular instance shown, is provided withcontact elements hereinafter more particularly described in connectionwith Figure 3. The blow out coil assembly 53 which includes the coil 54of Figure 3 and the laminated blow out iron legs 55, is mounted on theupper insulating back panel 56 also across the bars 14' and 15 and theupper portion of vertical supporting members iii and 11 and is supportedthereby.

it is spaced from the bars 10, 11, 32, 14, 15 by the upper insulatingback panel 56 which panel is secured across the bars 10, 11 and 32 asshown in Figures 2 and 3. Appropriate openings 59, 59 are provided inthe panel 56 to permit the terminal members 30 and 31 to projecttherethrough in a manner shown in Figures 1 and 3.

The arc chute assembly 57 is supported by the blow out assembly 53 andparticularly by the laminated legs 55 of the blow out iron which ridebetween the bracing bars 58, 58 on each side of the arc chute as shownin Figures 1 and 5, and as will be more specifically describedhereinafter in connection with Figures 1, 4 and 5.

As will also be hereinafter pointed out the front are runner 2913(Figure l3) of the arc chute is not connected in any way to any of theother elements of the circuit breaker but is brought into the circuit bythe proximity of the moving contact 20A thereto during the openingoperation. The rear runner 290A (Figure 13) of the arc chute 57 isconnected to the circuit breaker through the blow out coil mechanism 53by the clip arrangement indicated generally at 300 of Figures 1, 4, l3,and also hereinafter more specifically described. The are chute isentirely supported by the laminated legs 55 of the blow out iron on eachside, being retained in position by the latch assembly 61 (Figure alsohereinafter more specifically described.

The final unit assembly comprises the interphase barrier assemblyindicated generally at 63 of Figures 2, 8 and 9. The interphase barrierbeing supported at the rear end by resting on the cross bar 65 (Figure2) secured across the lower end of the panel 56 and by resting at thefront end on the angle iron 66 carried by the racking and indicatorassembly 43.

All of the elements of the circuit breaker as will be seen from aninspection of Figures 1 and 2, and of subsequent figures may beinexpensively made from ordinary sheet metal or cut from ordinary bars,and no complicated casting or machining operation is required, thusleading to great economy in the manufacture and assembly of the device.

Also from the previous discussion it will be seen that the assemblyoperation consists of a number of units as above described, each ofwhich may readily be stocked and kept in storage without consuming anundue amount of space and which may readily be assembled simply by a fewbolt or screw manipulating operations to interconnect an entire circuitbreaker from the unit assemblies.

The operating mechanism shown in the perspective front view of Figure 3in the parent Patent 2,613,299 issued October 7, 1952, comprisesessentially a simple switch operating mechanism with the addition of thenecessary tip unit trip-free operation and solenoid closing mechanismnecessary for automatic circuit breaker operation.

Lower terminal assembly The lower terminal assembly 31 shown in Figures1, 2 and 3, comprises a bar of copper 15%} insulated by an oblongBakelite tube 151 with a conductive inner lining into which it has beenpressed. The front end 152 supports the movable contact bridge assembly50 in a manner hereinafter specifically described, while the maindisconnect contacts 38 are secured to the rear end 154.

The lower terminal 31 has the side flanges 156, 156 secured thereto inany suitable manner, to cooperate with the movable contact arm as shownin Figure 3. In the usual procedure for insulating a terminal bar suchas that shown in Figures 1, 2 and 3, phenolic insulation material iswrapped around the bar and tightly pressed thereon. This is acomplicated process which must be performed on special machinery and bythose having special skills in the field.

In the present construction, instead of wrapping phenolic insulationtightly around the bar 150, the flat tube 151 is used, said tube beingprovided with a conductive lining 162. This tube is placed over the bar150 and then pressed into tight engagement with the bar to provide theinsulation cover therefor.

The principal reason for wrapping the insulation in the prior art wasthat no minute air pockets could be per mitted since at high voltagesthese would result in corona discharge, causing progressive dielectricdeterioration and thereby resulting in breakdown of the insulation.Conse quently great care was required in the wrapping of the insulation.

We have discovered that by using a sleeve of insulating material andmaking the inner surface of the sleeve conductive, the sleeve may simplybe pressed down around the tube to conform with the contour of the barand provide a completely engaging surface to surface contact thusavoiding any deleterious effects resulting from any minute air pocketsthat may remain. Thus where the prior cost of wrapping such bars was inthe neighborhood of $12.00 per bar and it was necessary to send the barout to be wrapped by special machinery, our invention makes possible theinsulation of the bar at the circuit breaker plant at a cost of about$1.50.

Upper terminal assembly The upper terminal assembly 30 shown in Figures1, 2 and 3 also comprises a bar 160 of copper having an insulatingsleeve 161 mounted thereover in the same manner as previously describedin connection with the lower terminal assembly of Figure 3.

The rear end of the bar 160 has the conformation 165 to receive and holdthe main disconnect contacts 38 shown in Figures 1 and 2. The front endof bar 160 has secured thereto the stationary main contact 167 and thestationary arcing contact 166 (Figure 3). The upper end of the frontportion of bar 160 has secured thereto the insulating blocks 165 and 168(Figures 1 and 3)., which have secured thereto the insulating plate 170having the upper slotted extension 170a. Connector 171 is secured in anysuitable manner to the insulating blocks 165 and 168 but is insulatedfrom the contact bar 160 and the arcing contact 166 and stationarycontact 167.

Connector 171 has a slotted or cut away portion 179 at its front endbetween which, and spaced from either edge, the forward end 208 of themovable contact arm 204 comes to rest when the contacts are inengagement as will be described hereafter.

Movable contact assembly In Figure 3, we have shown one of the contactarms 80. The contact arm 80 comprises a pair of copper bars 180, 181between which is secured, at the upper end by pin 205, the arcingcontact arm 205. The movable arcing contact arm 204 is held in properspaced relation by the spacer washers 184-184, all of which are forcedinto proper current carrying relation by the spring washers 233233. Theupper inside edge of the copper bars -181 carry special are resistingsilver alloy contact blocks 185 which comprise the main movablecontacts.

The lower ends of the bars 180 and 181 are provided with the registeringopenings to receive the pin 187 (Figures 1 and 3) which pin passesthrough the openings and through the slotted openings 188 (Figure 4) ofthe front end 152 of the lower terminal 31 which is received between thearms 180181.

The pin 187 is provided on each side with a lug 190 (Figures 1, 3 and 4)carrying the bar 191 which passes through openings 193a (Figures 3 and4) of the side flanges 156. Compression springs 193 on each side arecaptured between flanges 156 on each side and the lug 190 of pin 187 oneach side thus forcing the lower end or pivot of the contact arm outtoward the right with respect to Figures 1 and 3 at the pivot point 186.

The contact arm effectively pivots about pin 200 (Figures 1 and 3) whichis connected between the arms 181 and 180 and which carries the end oflink 51 connected 9 to contact operating arm 52. Thus, compressionsprings 193 forced the contact arm 80 to rotate counterclockwise aboutthe pin 200 within the limit of the length of slot 188 on the lowerterminal and thus forces the movable contact 185 into close wipingengagement with the stationary contact member 1167 (Figures 1 and 3).

In any position of the arm 89 other than the closed position of the arm80, compression springs 193 push the pin 186 over to the far right endslot 188 of the lower terminal of Figure 4. When the contact arm reachesthe closed position of the contact, the movable contact 185 bearsagainst the stationary contact 167 and as the link 51 forces pin 200 andcontact arm 80 into the closed position, the spring 193 yields becauseof the slope of the angular slot 188 to permit the wiping action tooccur between the contacts 185 and 167 and the contacts to close firmly.

The forward end 152 of the lower terminal of Figure 4 is provided withsilver alloy inserts 202, 202 to bear against the inner surfaces of arms180, 181 of contact arm 80. Thus it will be seen that no pigtails areused, but appropriate elements are used on pin 187 to squeeze the lowerends of arms 181, 180 against the insert contacts 202 on the lowerterminal.

The contact springs 193 are located close to the pivoted stud 187 whichis a distinct advantage because they are well away from arcing Zone. Theconnection of link 51 to the contact arms is at a point 200, as abovepointed out, well above the center point of the arms 80, so as to makethese contact blow-on contacts as explained in the followingdescirption.

In response to a rise in currents, magnetic forces developed in thesecontacts tend to increase contact pressure at all contact points. Thearcing contact arm 204 is pivotally mounted on the pin 205 between thecontact arms 180, 181 and the spacer washers 184, and is provided withan arcing contact element 206 and the horn 207. The lower end of arcingcontact arm 204 is connected by the floating pin 210 to the link 211which in turn at this lower end bears against the milled surface 212 ofthe milled pin 213 carried between the arms 180, 181.

Tension spring 215 connected between lug 216 and spring eye 217 isarranged to rotate link 211 clockwise around the bearing furnished bythe milled portion 212 of pin 213. The lug 216 is adjustably mounted onscrew 220 which in turn is received in the tapped opening 221 of pin 222carried between the arms 180, ,181. Rotation of screw 220 results inmoving lug 216 to change the tension of spring 215 and thus increase thebias thereof.

Spring 215 thus acts on links 211 to cause the toggle 211--210204 tocollapse in a direction to force the arcing contact 206 to the left. Thefull collapse of this toggle is prevented by the adjustment of screw 220which whichbears against the end 225 of arcing contact arm 204. Tensionspring 215, however, thus drives the arcing contact element 206 out tothe left with respect to Figure 3 where it will make contact with thestationary arcing contact 166 before the main contacts engage and whereit will maintain contact with the stationary arcing contact until afterthe main contacts have separated.

Since the center 205 of arcing contact arm 204 is well above the midpoint thereof, a blow-on action of the arcing contact occurs, also thusensuring that the arcing contacts will remain firmly in engagement untilthe main contacts have separated.

The position of the arcing tips 206 above the main contacts 167 forms anupward loop in the circuit which tends to initiate a blow out action tostart the arc upward when drawn.

In order to protect the lower terminal structure against any possibledefect in the arc chute or blow-out mechanism which would tend to drivean are down, an insulating shield 230 is provided secured to the screws183 and 10 flared out to protect the uninsulated portion of the lowerterminal bar 150.

Spring 215 ensures that the movable arcing contact will move intoengagement with the stationary arcing con tact as the contact arm beginsto open and before the main contact separates. The arcing contacts willthen stay in engagement for a substantial portion of the openingmovement depending on the setting of screw 220 (Figure 3).

Blow out assembly The blow-out assembly 53 comprising the coil 54 andthe laminated blow-out iron legs 55 already referred to in Figures 1 and2, is shown more specifically in Figure 3. The coil 54 is connected bythe lead 235 and bolt 236 (Figures 1 and 3) to the upper terminal bar160. The opposite end of coil 54 is connected by lead 238 to extension171a on contact bar 171 passing through a slot in the upper extension170a of insulating strip 170 (Figure 3). Coil 54 is wound on an ironcore 240 to which is secured the laminated blow-out iron legs 55 oneither side.

We have found that preferably four such side plates on each side /s"thick ensures a proper distribution of magnetic blow-out flux over thefull length of the side plates. Also we have found that in order toobtain a proper blowout flux without inserting too much impedance inseries with the are it is desirable that the coil 54 consist of 18 turnsof copper strips of x The side frame members 242, 242 (Figure 3) of theblow-out assembly are secured against the core 240 by bolts 243 whichalso secure the plates 55 against the core. The side frame members 242of the blow-out assembly have secured therebetween the upper block 245by means of pin 246 and the lower block (not shown) by means of pin 248and plat 249 by means of screws 250.

Blocks 245 and its corresponding lower block are provided with tappedopenings by means of which the entire blow-out assembly may be readilysecured to the frame of the circuit breaker. It will thus be seen thatthe entire blow-out assembly may be readily mounted on and removed fromthe circuit breaker as a single unit.

Arc chute The blow-out assembly serves as support for the arc chutedescribed in Figures 3, 5, 6 and 7. The are chute assembly 57 mountedabove the contact assembly provides for a positive and efficient arcinterruption. It consists of insulation side walls 257, front and backare runners 291 and 290 respectively (Figure 13) and a series of ceramicplates 260 (Figure 12) mounted in spaced relation transverse of the arcpath and a strong magnetic blow-out field to force the arc into the arcchute.

The sides 257 (Figures 5 and 7) have fastened at their lower portion,adjacent the arcing area, inner arc resisting insulating plates 269-269of special composition herein-after described. The are resisting plates269 are chamfered along their upper edges at 262262 to provide astraight locking edge for the cross plates 260 and the spacers 261. Thelower ends of the cross plates 260 and the spacers 261 are appropriatelyshaped to fit the chamfered edge 262.

As the arc is driven into the chute by the magnetic field, it passesrapidly through the arc extinguishing ceramic plates 260 which arerectangular in shape at the top and have a long tapered lower edgeextending from the center of one side of the plate to the lower corneron the opposite side of the plate. A ceramic spacer 261 is provided tosupport each plate and position it with respect to adjacent plates andforms with the long tapered surface of the plate, a triangular openingwith the apex at thetop for the passage of the arc. Each plate with itsspacer presents a decreasing area for the arc as it rises and graduallysqueezes it into a narrow slot 307.

The plates 260 are assembled alternately in an inter 1 1 lcaved relationand spaced from each other so that the long tapered surfaces cross atthe center of the chute directly above the path of the are as it travelsup the chute. As the 'arc passes the cross-over point of the plates itis forced into a zigzag or sinuous path gradually but rapidly increasingits length and bringing it into contact with the larger and larger coolsurfaces of the plates. The arc must thus bend around the edges of theplates which are effective in circuit interruption. The positive andefiicient arc interruption is affected by the cooling, lengthening andsqueezing of the are at numerous points all along its path.

Provision for the interruption of low current arcs is built into the arcchute. No moving parts or auxiliary equipment are necessary. Shortcircuit or normal overcurrents are extinguished before the moving archorn 207 passes the front arc runner 291. The arc formed by currents oflow value is extended in the chute beyond the front are runner 291 andeffectively cooled and deionized by a set of plates 322 (Figure 6)located in the current path.

Arc travel toward the front of the chute involves a transfer from thearc contact arm 207 to the forward arc runner 291. The absence of thereturn connection from this runner to the lower lead is a new feature inhigh voltage breaker design. Without this connection the dielectricstrength of the open breaker is not dependent upon the arc chute, whoseinner surfaces are bound to deteriorate through use. Without thisconnection, the arc between the contact arm 204 and runner 291 continuesas long as the arc exists. On high values of current the arc isextinguished before the contact arm 204 passes the runner 291.

Progress of the are up into the chute brings it in contact with thecross plates 260 which are shaped and assembled so as to cause the arcto follow a gradually increasing zigzag form, thereby securing a longarc length in a short length of chute. Maximum length in a crosswisedirection is realized at a point opposite with the top of the blowoutiron side plates 55 where it enters a narrow confining slot 367. Thelength of the plates 260 above this point is used to cool and deionizethe incandescent gases which result.

When the current to b interrupted is of low value, low magnetic actionexisting at that time is still suflicient. The are is extended by thelong travel of the arcing tips and cooled by the specially locatedplates 322 below the front arcing horn 291.

The plates 260 are held in position in the arc chute by the insulatingcross-bar 263 (Figure -7, 13) carried in the slot 264 of the end pieces267. Insulating cross-bar 263 is securely fastened by bolts 265, 266respectively, at the front and back end pieces 267 of the arc chuteassembly 57 which extend up above the side plates 257.

The side plates 257 are connected together at the front and back end ofthe arc chute by bolts 268 which connect them to the front and backstrips 267. The side plates are provided with insulating bracing bars 58secured thereto by the bolts 268 and spaced apart by the width of thelaminated blow-out iron legs 55.

The materials used in the construction of the arc chute play anextremely important part in the performance of the circuit breaker.

The side plates 257 are made of Bakelite with a layer of fibre on eachside. During interruption not only full voltage is applied to theseplates but frequently switching surges of very high value areencountered. The high insulating value of Bakelite is desired but italone would not be satisfactory since it has the characteristic ofcarbonizing and tracking it any are or high temperature arc gases comesin contact with it. Consequently, the Bakelite is coated with fibrewhich does not have this characteristic. Furthermore, an arc-resistinginsulating varnish is applied to the fibre to keep it from absorbingmoisture. Furthermore, the spacers 261 for the cross-plates 260 12completely line the inside of the are coming in contact with the sideplates at any point.

The material of which the cross plates 260 and the spacers 261 are made,determines to a large extent the ability of the breaker to interruptcurrents. The least expensive material that is at all suitable for thisapplication is the asbestos cement board called Transite. This materialgives fair operation and for low interrupting capacities is quitesuitable. In an effort to increase the interrupting capacity, numerousmaterials were tried. Gas forming materials such as fibre were found tobe unsatisfactory as they increased the display incident to circuitinterruptions and the excess gas had a tendency to initiate arcing inother parts of the breaker. Inert materials were better. Porcelain,while quite good was too fragile and could not be manufactured in thinplates with sufiicient accuracy to make it practical.

By far the best material found was the glass bonded mica consisting ofmica dust and glass fused and pressed at high temperature and pressure.It is inert at the temperatures encountered in the arc chute, anexcellent insulator, does not absorb moisture and is a non gas formingmaterial. This material when used for the arc plate and spacersincreased the interrupting capacity to more than twice the value shownby other materials. It is used not only for the cross plates 260 andspacers 261 but also for the arc resisting plates 269 that come incontact with the arc.

The are chute may be mounted in position by being slid on to thelaminated blow-out iron legs 55 so that the reinforcing bars 58, 58 actas runners to receive the laminated legs 55 in the manner shownspecifically in Figure 1, thus holding the arc chute in position.

In order to insure a further distribution of magnetic blow-out flux downinto the region of the contacts, an additional iron plate 274)(Figure 1) is provided on each side of the arc chute secured to thebracing bars 58 by screws 2'71 and having extension 272 extending downinto the region of the contacts outside the plates 57.

The blow-out flux through the laminated blow-out iron legs 55 is alsocommunicated to plate 270 and by extension 272 is communicated down intothe region of the contacts to increase the blow-out effect in thatregion. The runners or bracing bars 58 on one side of the arc chute areprovided with the bronze springs 280 connected as shown in Figure 5between the runners or bracing bars 58 by screws 281 and a latchassembly 61 secured thereto in any suitable manner as by the screws 283,283 (Figures 5 and 6) and having a projection 282 which engages acorresponding detent 284 in the laminated iron leg 55 (Figure 1). Thusthe are chute is supported by the laminated legs 55 between runners 58on each side and is latched in position by the latch assembly 61engaging detent 284 in laminated legs 55. To remove the arc chute it isonly necessary to press in the latch assembly 61 to disengage the detent284 from laminated iron legs 55 so that the arc chute may he slid out.As already stated, the arc chute is provided with a back are runner 290and a front arc runner 291 converging below the arc chute and toward thecenter in the region of the con tacts, the front are runner 291 havingextension 291B toward the contact and the rear arc runner 290 havingextension 290A toward the contacts and the further rearward extension293.

The portion 171A (Figure 3) of the upper terminal to which lead 238 ofthe blow-out coil is connected is also provided with the spring clip 300(Figures 1 and 3) to receive the rearward extension 293 of the rear areborn 290 of the arc chute'57. Thus no special connection need be madefor the arc chute; but when the arc chute is slid into position, therear extension 293 of the rear arc horn 290 moves into the spring clip300 and the rear arc horn is thus connected to the end 238 of blowoutcoil 54.

The section 29GB of the rear are born rests on plate 171 to obtainfurther contact to the rear arc horn 290. Thus when the section of thearc on the stationary arcing contact jumps to section 290A of the reararc horn, the current path is from terminal 30, bolt 236 to lead 235 tocoil to lead 238 to section 171A of member 171 and spring clip 300. Thenfrom spring clip 300 to section 2901) of rear arc horn 200. Then throughthe arc chute to the movable arcing contact from the front arc runner291 as hereinafter more specifically described.

The cross plates 260 as shown particularly in Figure 6 are each of aninsulating non-carbonizing material, preferably a glass bonded, micaceramic material or of a material known as Transite. These plates arelongitudinal members as shown in Figures 6 and 7 having a curve atsection 303 of a very large radius; upward of this position they have acurve 304 of smaller radius; and above that position have an extension305 entering the notch 260 and closing off that side of the plate.

The side of each plate opposite the curve is flat. When the arc is firstdrawn it is driven up by the blow-out mechanism into the notch 210 ofV-shaped cross-section formed by the curves 303304 of the alternatelyarranged plates. As the arc is driven up further beyond the apex of thenotch, it is caused to zigzag laterally in flowing past the curves 304of the alternately arranged plates. it thus passes through therelatively narrow notch 307 on one side of one plate and then through asimilar relatively very narrow notch on the opposite side of thealternate plate and back and forth laterally through the arc chute.

If the arc is not extinguished when the arc has reached this point, themagnetic blow-out blows the are up still further past extension 305where in addition to the lateral zigzagging and lengthening of the arc,the arc is zigzagged vertically. This combination of extreme lateralzigzagging with vertical zigzagging of the arc ensures extinguishment ofthe are before the top of the arc chute is reached. The combination oflateral zigzagging with vertical zigzagging limits the upward travel ofthe arc.

Thus it will be seen that one of the essential elements of the arc chuteherein described is first the lateral zigzagging of lengthening of thearc as it is blown up into alternating thin narrow slots on each side.Thereafter the portion of the are between the cross-plates 260 is freeto move up to superimpose on the lateral zigzagging or lengthening ofthe arc, a vertical zigzagging or lengthemng.

Also it will be seen that there is no connection whatever between thefront arc horn 291 and the lower terminal or any other terminal when thecircuit breaker is closed or open.

The advantage of the arc chute thus described will thus be obvious. Theschematic view of Figure 13 further illustrates the advantages of mynovel are chute.

With the circuit breaker closed, the current passes from upper terminalbar 30 through the main contacts and contact arm 80 to the lowerterminal bar 31. On the occurrence of overload conditions resulting intripping of the circuit breaker, a change in current occurs in which theinitial opening movement of the contact bar 80 pulls the main movingcontacts apart but retains the arcing contacts in engagement so that thecurrent path is now through the arcing contacts.

When the moving are tips 206 first separate from the stationary contact166 an arc is drawn between contacts 166 and 206. The blow up action andthe ionized gas from this arc drives the arc upwardly along contact 166in an arcaute form until an arc is established between the contact 166and U-shaped notch 171-B and thence from the U-shaped notch 171-B to theforward position 203 of the arc horn 207. The arc between the arcingcontacts 166 and 206 is in parallel with the arcs between contacts 166to 171-B to 208. Since the impedance of the gap between 166 and 208 ismade to be less than the gap between the arcing tips 14 166 and 206,after the latter has moved a predetermined distance, the are between thearcing tips 166 and 206 is immediately extinguished.

The shapes and the space between the U-shaped piece 171-B and thestationary arcing tip 166 is such that the arc thereacross is struck andcontinues. This arc is in parallel with the circuit through the windingsof the blow-out coil 54.

The voltage drop across the blow-out coil 54 is in proportion to thecurrent flowing in the circuit. When the breaker is opening high shortcircuit currents, the voltage might be as high as 2,000 volts if all thecurrent flows through the blow-out coil 54. This does not occur sincethe voltage will maintain the are between 171-B and 166. The current inthe breaker therefore divides; part of it passing through the blow-outcoil 54 and part of it through the are between 17143 and 166. Thedivision of current in these two paths is inversely proportional to thefault current value and to the voltage drop in the blow-out coil 54, i.e., the current flowing in the blow-out coil is of a value such the dropin the coil equals the drop across the gap in parallel. The division ofthe current in the two paths is therefore diiferent at differentoverload current values. For instance, at low current values, most ofthe current will pass through the blow-out coil since the voltage acrossthe blow-out coil assembly 53 is low and the arc is scarcely maintained.At higher current values flowing through the circuit breaker, however,proportionately less of the current must flow in the blow-out coil 54 tomaintain the voltage drop across the coil equal to the voltage dropacross the gap and accordingly more current in proportion is shuntedthrough the arc.

This is a very desirable feature since the circuit breaker must operateon all current values up to its rating. A blow-out coil can inaccordance with this arrangement, be designed to be effective at lowcurrent values and still be effective at high current values withoutrequiring it to carry the full short circuit current. may be made ofsmaller wire, more turns and less bracing without danger of its burningout or being distorted by the high currents.

Another advantage of this arc transfer method of inserting theblow-out'coil is that the blow-out coil 54 is not in the circuit at anytime except when opening a circuit. Therefore, it is not required tocarry any current continuously.

Those skilled in the art will also recognize that the performance of thebreaker may be varied for a wide range of current values by the designof the arc gap between 171-B and 166. The impedance of this gapdetermines the current flowing in the blow-out coil 54. By increasing ordecreasing the length of this gap, its impedance is afiected and thecurrent in the blow-out coil 54 is for any short circuit current valueincreased or decreased. Further any deionizing elfect on this arc as theresult, for instance, of blowing it into narrow slots 63 or againstrough edges of insulating material, will increase the arc impedance andalso alfect the blow-out characteristics of the breaker.

It will be noted that extension 272 of the iron plate 270 (Figures 5 and6) comes down on each side of the arc chute adjacent to the arcs between171-B and 208 and also between 171-B and 166. This increases the fluxdensity at this point. The effect on the arc between 171-B and 208 whichis horizontal is to drive it rapidly up the runners 290, 291 and intothe arc chute 57. The effect on the are between 171-B and 166, which isvertical, is to drive it back against the insulating and heat resistingblock 168. This insulating block may be provided with slots, grooves,holes 163 or other cooling means to deionize the arc and aflfect theblow-out characteristics of the breaker. It will be apparent that thesize, shape and spacing of the extensions 272 will also afiect theblow-out characteristics.

The blow-out coil It will also be noted that the conductive bar 171 hasa U notch indicated generally at 171-13 therein, in which the upperarcing horn 207 registers, thus provided for simplified transference ofthe arc to the contact bar .171 and hence to section 290a of the reararc runner 290 of the arc chute 57.

On further opening of the contacts, the arc is blown up into the arcchute, the current path including contact bar 30 through bolt 23.6 andlead 235 through the blowout coil 54 and then through spring clip 300and conducting bar 171 to the arc runner 290. The are then passesthrough the arc chute to the front are runner 291, then to the arcinghorn 207 on the movable arcing contact and down through the movingcontact structure 80 to the lower terminal 31.

At this time, the gap between the arcing horn 207 and section 29113 ofthe front are runner is small enough to permit transfer of the arc tothe front are runner as the contact moves past it during opening. Theare should be blown out very shortly thereafter.

In the event of an opening of the circuit breaker with relatively lowcurrents where there is relatively very low blow-out flux, then the arcmay continue to be drawn until the movable contact reaches the positionsshown in Figure 13, the are extending from section 29113 of arc runner291 below this are runner to arcing horn 207 on the moving arcingcontact 204 and there the arc is cooled and blown out through theauxiliary arc chute 320 (Figure 13) comprising the insulating sideplates 269 carrying between them the spaced insulating plates 322 whichare spaced by washers 323 on bolts 324 which secure the plates 322 inposition and also secure the entire auxiliary arc chute 320 between themain side plates 257 of the arc chute 57.

It will thus be seen that on opening of the circuit breaker underrelatively high overcurrent conditions, the arc is blown up to theposition shown in Figure 16 and blown even high and extinguished. Inopening the circuit breaker on relatively low currents, at longer arcingpath is relied upon, the double are shown in Figure 13 being drawn wherethe upper section of the are is extinguished by the cooling platesalready described in the main arc chute, and the lower section of thearc is extinguished by the auxiliary arc chute 320.

The insulating shield 230 above described in connection with Figure 3prevents a low current are from being blown down accidentally contactingthe terminal 31. lograph tests have shown that rates of arcextinguishment ranging from .58 cycle at 63,200 lcva. (4200 volts) to a2.5 cycles at 3728 kva. (5000 volts).

The arcing time may be even slower at lower voltage and current values,but these values illustrate the etticiency of our novel device.

Interphase barriers The interphase barrier assembly 63 is a completestructure shown in Figures 2, 8 and 9 sufficiently light to be easilyhandled by one man. Preferably it is installed as a complete unit asshown in Figure 2, but in the event storage space is at a premium, theinterphase barrier may readily be stored knocked down to be assembled bydriving a number of screws through registering openrngs.

The interphase barrier assembly as shown in Figures 2, 8 and 9 comprisea pair of side plates 330 connected together by the front plate .332.Corner pieces 335, 335 are provided at each side to receive the screws336, 336 of the front plate 332 and the screws 337, 337 of the sideplates 330.

Further reinforcing strips 340 are secured to the front panel 332 byscrews 341 to provide a means of securement and spacing for theinterphase barriers 345. An additional notched top strip 350 is securedto the front panel 332 at the upper end, the notches therein providingspacing elements for the interphase barriers. The rear Oscil-.

16 of the interphase barrier may have cross bars 352, 352 securedthereacross by screws 353 entering into the opposite outside panels 330.These cross bars may also be notched to receive and position theinterphase barrier elements.

Each hole or space in the interphase barrier may have secured thereinbetween appropriate reinforcing blocks 360 the horizontal barrier 361 toprevent ionized and heated gasses from being down in the arc chute.

Since many variations and modifications of our invention should now beobvious to those skilled in the art, We prefer to be bound not by thespecific disclosure herein contained, but only by the appended claims.

We claim:

1. In a circuit breaker having a pair of cooperable contacts with anengaged and disengaged position; means for effecting disengagement ofsaid contacts; a main arc chute having a plurality of spaced arc platesmade from a ceramic material; means for blowing an are formed betweensaid pair of cooperating contacts into said main arc chute; said mainarc chute having a front and back are runner; said back are runnerpositioned in the area adjacent said cooperable contacts when saidcontacts are in engaged position; said front arc runner positionedadjacent one of said cooperable contacts when said contacts are in saiddisengaged position; an auxiliary arc chute mounted below said front arerunner; the are formed on disengagement of said contacts in response torelatively low current faults being blown into said auxiliary arc chute.

2. In a circuit breaker having a pair of cooperable contacts having anengaged and disengaged position; means for effecting disengagement ofsaid contacts; a main arc chute having a plurality of spaced arc platesmade from an insulating material; said main arc chute having a front andback are runner; an auxiliary arc chute mounted below said front arerunner; said auxiliary arc chute having a plurality of spaced arc platesmade from an insulating material; said are plates of said main arc chuteextending in a direction perpendicular to the direction of said areplates in said auxiliary arc chute; the are formed on disengagement ofsaid contacts in response to relatively low current faults being blowninto said auxiliary arc chute.

3. In a circuit breaker having a pair of cooperable contacts with anengaged and disengaged position; means for effecting disengagement ofsaid contacts; a main are chute having a plurality of spaced arc platesmade from a ceramic material; means for blowing an are formed beweensaid pair of cooperating contacts into said main arc chute; said mainarc chute having a front and back are runner; said front and back arerunner converging below the arc chute and toward the center in theregion of said pair of cooperable contacts; an auxiliary are chutemounted below said front are runner; the are formed on disengagement ofsaid contacts in response to relatively low current faults being blowninto said auxiliary arc chute.

4. In a circuit breaker having a pair of cooperable contacts with anengaged and disengaged position; means for effecting disengagement ofsaid contacts; a main are chute having a plurality of spaced arc platesmade from a ceramic material; means for blowing an are formed betweensaid pair of cooperating contacts into said main arc chute; said mainarc chute having a front and back are runner; said front and back arerunner converging below the arc chute and toward the center in theregion of said pair of cooperable contacts; said bacs arc runner adaptedto be removably secured to a blow out means, an auxiliary arc chutemounted below said front are runner; the are formed on disengagement ofsaid contacts in response to relatively low current faults being blowninto said auxiliary arc chute.

5. In a circuit breaker having a pair of cooperable contacts with anengaged and disengaged position; means for efiiecting disengagement ofsaid contacts; a main arc chute having a plurality of spaced arc platesmade from a ceramic material; means for blowing an are formed betweensaid pair of cooperating contacts into said main arc chute; said mainarc chute having a front and back arc runner; said front and back arerunner converging below the arc chute and toward the center in theregion of said pair of cooperable contacts; said back arc runner adaptedto be removably secured to a blow out means; said front arc runner beingspaced from said cooperable contacts when said cooperable contacts arein said engaged and disengaged position; an auxiliary arc chute mountedbelow said front are runner; the arc formed on disengagement of saidcontacts in response to relatively low current faults being blown intosaid auxiliary arc chute.

6. In a circuit breaker having a pair of cooperable contacts with anengaged and disengaged position; means for effecting disengagement ofsaid contacts; a main arc chute having a plurality of spaced arc platesmade from a ceramic material; means for blowing an arc formed betweensaid pair of cooperating contacts into said main arc chute; saidplurality of arc plates spaced in a direction parallel to the are; saidmain arc chute having a front and back are runner; an auxiliary arcchute mounted below said front are runner; said auxiliary arc, chutehaving a plurality of spaced arc plates made from an insulatingmaterial; said spaced arc plates of said auxiliary arc chute extendingin a direction perpendicular to the arc; the are formed on disengagementof said contacts in response to relatively low current faults beingblown into said auxiliary arc chute.

References Cited in the file of this patent UNITED STATES PATENTS1,713,229 Hewlett May 14, 1929 1,872,387 Baker et a1 Aug. 16, 19322,147,430 Ellis et al. Feb. 14, 1939 2,442,199 Dickinson et al May 25,194-8

